Psychology 202a Advanced Psychological Statistics September 3, 2015

The show so far Last time we talked about: –variables –distributions –grouping –ways of understanding the shape of a distribution

Peabody Distribution ValuesFrequency 55 – – – – – – – – – – 1041

Software We saw that functions in R tend to use fairly intuitive names (e.g., sort(), stem()). We were about to introduce SAS and begin a discussion of descriptive statistics. Let’s do that now.

Ways of understanding shape Graphics. Descriptive statistics.

Histograms A histogram is a picture of the frequency distribution: –group the data (7 to 15 intervals)‏ –identify real limits and midpoints of intervals –draw “histobars” over the intervals –use informative labels

Peabody Distribution ValuesFrequency 55 – – – – – – – – – – 1041

Histograms in R hist(Peabody) R has done a pretty good job: –informative labels –reasonable number of intervals but the limits R chose for the intervals are a little strange help(hist)